Amino silanes are commonly used as adhesion promoters in adhesives and sealants, and as coupling agents in compositions used in the plastics and glass-fibers industries and in foundries, in fabric treatment compositions, and in personal care products.
In particular, secondary and tertiary amino functionalized silanes are useful as coupling agents in the fiberglass and automotive glass industries. Currently the best technology for producing functionalized amino silanes is either through hydrosilation of a functionalized allyl amine, through reductive amination of a primary amino silane, or by nucleophilic substitution of gamma-chloropropyltrialkoxysilane. Unfortunately, functionalized allyl amines are not readily available, and are often quite expensive when they are available. Reductive aminations, on the other hand, are limited to symmetrical secondary amines, and often occur in such low yields that they are cost prohibitive, while nucleophilic substitution generates one equivalent of hydrochloride salt that must be recycled or disposed of.
Primary amines are one of the more reactive functional groups in organic chemistry and are known to react rapidly with a variety of carbonyl containing compounds. In the case of aldehydes and ketones, nucleophilic addition and dehydration results in an analogous imine structure that forms almost quantitatively at room temperature. Subsequent reduction of the imine functionality has been shown to provide an economical route to secondary amines. While the application of this methodology to amino silanes has already been reported in the patent literature, the direct reaction of silanes with aldehydes or ketones inevitably leads to the formation of siloxanes and lower yields.